The field of the present invention is that of an arrangement of an internal combustion engine with a variable timed camshaft. More particularly, the present invention relates to an arrangement of a pressurized fluid supply and filter for an automotive internal combustion engine with a variable timed camshaft.
Automotive vehicle engines with reciprocal pistons typically have a plurality of cylinder combustion chambers with the reciprocating pistons being mounted therein. Each piston is pivotally connected with a piston rod, which is pivotally connected with a crankshaft. At an end of the crankshaft a timing gear is mounted. Typically, each cylinder has at least one intake valve and one exhaust valve. Both the intake valve and the exhaust valve are spring loaded to a closed position. Each intake and exhaust valve is associated with a rocker arm. To operate the valves, the rocker arms are moved by a set of contacting cam lobes. The cam lobes are mounted on an elongated member known as a camshaft. Attached at an extreme end of the camshaft is a camshaft pulley. The camshaft pulley is powered by the crankshaft via a timing chain or belt which is looped over the camshaft pulley and a crankshaft timing gear. Accordingly, the camshaft is synchronized with the crankshaft and the timing of the opening and closing of the intake and exhaust valves is fixed with respect to the position of the piston within the cylinder combustion chamber.
In an effort to improve the environment by decreasing polluting emissions and increasing vehicle gas mileage, it has become desirable to allow the timing of the cylinder valve operation to vary with respect to the piston position within the cylinder chamber. To provide for the variable valve timing operation, a variable cam timing unit (VCT) provided on the camshaft.
An example of a VCT is a dual oil feed vane-type VCT. A dual oil feed vane-type variable cam timing unit provides an inner member or hub that is fixably connected to an end face of a camshaft. The hub has a series of vanes which are captured in cavities or pressure chambers provided in an outer member which is concentrically mounted on the hub. The outer member incorporates the camshaft timing pulley. The vanes circumferentially bifurcate the pressure chambers into an advance side and a retard side. A spool valve, fluidly communicative with the pressure chambers via the inner member and the camshaft, controls the fluid pressure in the advance side and retard side of the pressure chambers. Accordingly, the angular position of the timing pulley versus the crankshaft can be varied by controlling the fluid in the advance and retard pressure chambers.
The VCT utilizes engine lubricating oil pressure and flow to phase the camshaft. The VCT must meet minimum phase speed requirements to achieve desired fuel economy, emission benefits, acceptable drivability, and the avoidance of stall conditions.
Most automotive engines are formed from a cast iron or aluminum engine block. The lower portion of the block forms the combustion chamber and a crankshaft cavity. An upper portion of the block forms a top portion of the combustion chamber and is commonly referred to as the cylinder head. The head also mounts the crankshaft and idler arms. To lubricate the rotating portions of the engine, which are mounted in the cylinder head, there is provided a generally vertical or vertically inclined lubrication passage that extends from the main oil gallery. The main oil gallery is typically located in the lower portion of the engine block laterally above the crankshaft. The generally vertical passage extends to an intersecting vertically extending passage formed in the cylinder head. The vertically extending passage in the cylinder head is intersected by a horizontally extending cylinder head main oil gallery. The cylinder head main oil gallery then feeds off to the separate camshaft bearings and idler arms and other various lubrication areas. To prevent excessive oil going to the cylinder head main oil gallery there is typically provided a restrictor, which is often incorporated inside the head gasket between the lower portion of the engine block and the cylinder head. The restrictor limits the flow of oil to the cylinder head and therefore ensures the proper flow of lubricating oil to the other lubrication areas located within the lower engine block portion.
VCT systems typically have a solenoid that feeds the pressurized oil to the VCT unit on the end of the camshaft. A filter is required for the oil which is fed to the VCT spool valve and the VCT unit to protect them from damage from contaminants which can pass through the main engine oil filter. Additionally since the VCT unit in certain phases of engine operation can demand the maximum available pressure (15 psi gage) and flow output of the engine oil pump, it is desirable that the VCT supply passage to the solenoid in the VCT system be free of restrictions as possible.
Typically the supply passage which feeds the solenoid for the VCT control valve intersects the aforementioned generally vertically extending lubrication passage which connects the main oil gallery with the cylinder head main oil gallery. Prior to the present invention, the filter was placed within the lubrication passage within the cylinder head where the generally vertical lubrication passage intersected with the VCT oil supply passage. After filter insertion, a restrictorxe2x80x94which was typically a plug with a predefined hole drilled thereinxe2x80x94was placed within the vertical passage. The use of a plug was disadvantageous for several reasons. Unlike the restrictor, which was incorporated into the head gasket, a plug provided another part to the assembly process, and had a risk of being misassembled or inadvertently omitted. Further, the restrictor was typically a polymeric substance which, over long periods of exposure to high temperatures and lubricating oil, tended to lose some of its desired design material characteristics. Finally, the addition of the plug to the restrictor added to the cost of manufacturing the engine.
The insertion of a restrictor could be eliminated if a separate lubrication passage was provided exclusively for the VCT unit. However, a separate exclusive oil lubrication passage would significantly add to engine manufacturing costs.
It is desirable to provide a restrictor at a lower cost for an automotive engine having a VCT unit. It is desirable to provide a restrictor which during the assembly process does not carry the risk of being misassembled or inadvertently omitted.
To make manifest the above delineated and other desires, revelation of the present invention is brought forth. In a preferred embodiment the present invention provides an automotive engine arrangement having a VCT unit wherein the restrictor is incorporated within the VCT unit oil filter. The arrangement of the present invention allows for a filter unit to be installed in the head of an automotive engine and wherein placement of the filter in the appropriate location automatically installs the restrictor. Since the restrictor is incorporated inside the VCT filter, no additional parts are required. Incorporating the restrictor in the filter eliminates any requirement for the assembly of a separate restrictor.
It is an advantage of the internal combustion engine of the present invention to provide a VCT filter that incorporates a restrictor.
Other advantages of the invention will become apparent to those skilled in the art upon a reading of the following detailed description and upon reference to the drawings.